An ignition apparatus is known which includes an ignition coil equipped with a primary coil and a secondary coil and a spark plug connected to the secondary coil, and works to input energy to the spark plug by means of electromagnetic induction arising from energization and deenergization of the primary coil, thereby creating spark discharges.
Japanese Patent First Publication No. 2014-218995 discloses an ignition apparatus which is designed to continue to develop sparks once a spark is initiated. The ignition apparatus is equipped with a first and a second circuits, as described below.
Specifically, the first circuit energizes or deenergizes the first coil to start producing sparks in the spark plug. The first circuit connects a plus (+) terminal of a battery and a plus terminal of the primary coil, connects a minus terminal of the primary coil to ground, and has a discharge start switch (which will be referred to as a first switch) disposed on a minus side of the primary coil.
The second circuit works to produce a flow of electrical current through the primary coil in a direction opposite that produced by the first circuit during the spark initiated by the first circuit, thereby keeping a flow of electric current through the secondary coil in the same direction as that initiated by the first circuit to continue input of energy to the spark plug, thereby maintaining the production of sparks. The second circuit has a switch (which will be referred to below as a second switch) which is disposed, for example, between the primary coil and an ignition switch and works to supply or block electric power to the primary coil from a step-up circuit.
The electrical energy generated by the step-up circuit is inputted by turning on or off of the second switch to the negative side of the primary coil to continue to produce sparks, thereby reducing load on the spark plug and saving consumption of electrical power.
The ignition apparatus for internal combustion engines is required to minimize a variation in time interval between start of discharge of sparks and ignition of fuel (which will also be referred to below as ignition variation) in order to minimize combustion fluctuation. The ignition variation may be decreased by increasing the amount of energy inputted to the spark plug in all combustion cycles. The increase in input amount of energy, however, results in increases in load on the spark plug and consumption of electric power. How to reduce the ignition variation without increasing the input amount of energy is, therefore, sought.
Japanese Patent First Publication No. 2013-024060 teaches an ignition apparatus for internal combustion engines designed to control the so-called blowout. The blowout, as referred to herein, is a phenomenon where a path (which will also be referred to below as a spark path) of a spark is extended and then cut by gas flow, so that a spark occurs again. Japanese Patent First Publication No. 2013-024060 is, however, silent about the problem of the ignition variation and does not suggest how to reduce the ignition variation.